[0001] The invention relates to a filter assembly, comprising a filter head including a
screw thread and a container for receiving a filter element, the container being detachably
and sealingly secured to the filter head, adjacent to the screw-thread.
[0002] In many filter constructions, assemblies are provided which include a removable canister
which houses the filter element. Often in industrial filtering applications, pressure
within the filter can reach 2,000 p.s.i. (140 kg/sq cm) or more. To protect against
leakage at the area joining the canister to the filter body or head, the canister
must be tightly and securely held to the filter head. A common solution to the problem
of providing a tight and secure assembly which prevents leakage is to provide compression
seals or other gasket-type sealing members between the canister and the filter head.
[0003] For proper operation of the filter, it is necessary that a schedule for periodic
maintenance be followed. To maintain the integrity of the seals through multiple disassemblies
for the purpose of replacing the filter element, different coupling mechanisms between
the filter head and canister have been suggested. One such coupling is shown in US-A-4,316,801
which discloses a jackscrew connection between the filter head and canister. Wear
of the seal between the filter head and canister is minimized since the canister does
not rotate relative to the filter head as it is removed or replaced. Instead, the
canister is jacked on and off the filter head by the jackscrew which is rotatably
mounted on the canister.
[0004] Unfortunately, even with the arrangement disclosed in US-A-4,316,801, many combined
factors can contribute to a condition in which the canister is difficult to remove
from the filter head. One factor is the tight engagement between the canister and
filter head which is required to prevent leaks at high pressure operation. Also, the
filter is often exposed to environmental conditions resulting in corrosive build-up
at the mating joint of the canister and filter head. High internal fluid pressure
is another factor which may contribute to difficult canister removal by causing expansion
of the sealing members which results in an even tighter engagement between the filter
head and the canister. Finally, in some applications, the filter may be exposed to
thermal cycling which expands and contracts filter parts into an even tighter engagement
than originally achieved. Because of this difficulty, periodic maintenance has sometimes
been ignored. As a result, the filter becomes too clogged to pass fluid, which causes
a safety pressure relief valve to open and allow the fluid to bypass the filter element.
While the fluid system continues to function, the fluid no longer is cleaned of the
contaminants. As a consequence, the useful life of the fluid system is shortened and
the system integrity compromised.
[0005] In an attempt to free up a seemingly frozen connection between the canister and the
filter element, ad hoc procedures have been used such as vibrating the joining area
between the filter head and canister by firmly tapping the filter assembly. Repeated
use of such a procedure can damage the structural integrity of the filter assembly.
In addition, special tools, such as strap wrenches, are typically required to tighten
or loosen a filter canister, or a jackscrew such as is disclosed in US-A-4,316,801.
The difficulty and need for special tools to loosen the canister creates a condition
which discourages periodic disassembly of the filter for replacement of the filter
element.
[0006] The problem to be solved by the present invention is to provide a filter assembly
which can readily be assembled and disassembled without the need for especially adapted
tools such as are customarily required.
[0007] This problem is solved by the provision of an annular screw-threaded member screwed
to the screw thread of the head and having spaced abutment means, the head also having
an abutment, both the abutment of the head and the abutment means of the member being
engageable by an elongate member whereby a torque can be exerted on the annular screw-threaded
member to move it circumferentially relative to the head and permit relative motion
of the container along the axis of the screw-threads.
[0008] A filter assembly embodying the invention will now be described, by way of example,
with reference to the accompanying diagrammatic drawings, in which:
Figure 1 is a partial cross-sectional view of the filter assembly embodying the present
invention;
Figure 2 is a side view of the filter on line 2-2 of Figure l; and
Figure 3 is a plan view of a jackscrew embodying the present invention.
[0009] Turning now to the drawings, and referring first to Figure 1, there is illustrated
a filter assembly comprising a filter head 11, a filter canister or other container
13 and a jackscrew 15 or other annular screw-threaded member for coupling the canister
and filter head into tight engagement. In order to allow the canister 13 to be jacked
into engagement with the filter head 11, the jackscrew 15 is mounted on the outer
surface of the canister 13 and is free to rotate about the canister, but not free
to move longitudinally. The jackscrew 15 is generally annular in shape with an inside
diameter large enough to permit free rotation about the cylindrical canister 13 and
with a flared edge 15a which forms an outwardly radial projection. In order for the
jackscrew 15 to mate with the filter head 11, its outer annular surface is threaded.
The external thread of the jackscrew 15 mates with an internal thread in a cavity
in the lower portion of the filter head 11. Alternatively, though not preferred, the
jackscrew 15 could be provided with the internal threads, and the filter head 11 with
the external threads, similar to the arrangement in US-A-4,316,801.
[0010] To prevent movement of the jackscrew 15 along the longitudinal axis of the canister
13, an annular retainer ring 17 is secured, by welding or another suitable method,
to the canister just under the flared edge 15a of the jackscrew. The annular retainer
ring 17 also provides a surface against which the jackscrew 15 can bear to exert a
downward force on the canister. A ridge 13a at the top of the canister housing above
the jackscrew 15 creates a diameter greater than the inside diameter of the jackscrew
against which the jackscrew can bear to exert an upward force on the canister. Accordingly,
the jackscrew 15 is not only free to rotate about the canister 13 in a manner similar
to a wheel rotating about its axle, but is adjacent to upper and lower bearing surfaces
to effect the jacking action, described below.
[0011] When first engaging the canister 13 into the filter head 11, the canister ridge 13a
serves to pilot the threads of the jackscrew 15 into correct engagement with the threads
of the filter head 11, thus simplifying assembly and reducing the chance of cross-
threading, especially in the case of large filter assemblies. Once the two threaded
portions are mated the jackscrew 15 is screwed into the filter head 11 to jack the
canister 13 into tight engagement with the filter head. To complement the tight engagement
and to ensure the prevention of leakage, a gasket 19 is provided in the side wall
of the filter head circular cavity receiving the canister 13 and jackscrew 15. Since
the canister 13 is not rotated as it is mated with the filter head 11, the gasket
19 provides a good, durable seal which can withstand multiple servicings of the filter.
[0012] In order to stabilize the filter element 23 during operation and to automatically
free it as the jackscrew 15 jacks the canister away from the filter head 11, a helical
spring 21 is provided between the filter head and the filter element 23 to force the
latter against the bottom portion 13b of the canister. Cooperating with the helical
spring 21 is an annular platform 25 which mates with the top of the filter element
23 and compresses the helical spring 21 as the canister 13 and filter element are
jacked into the filter head.
[0013] In operation, fluid to be filtered passes through an inlet port 27 into an inlet
flow passageway 30 and into the canister interior 32. When the filter element 23 is
being replaced or when other areas of the fluid system are being serviced, a plug
33 can be removed which exposes the passageway 30 for the purpose of adding fluid
or allowing air to escape. The fluid passes through the filter element 23 and into
the central region 34. In the process of passing through the filter element 23, contaminants
are deposited in the element, leaving the fluid exiting the element into the central
region 34 in a cleaner condition.
[0014] From the central region 34 the fluid flows up through an anti-drain poppet valve
36 comprising a valve seat 36a, valve 36b and a helical compression spring 36c. Fluid
pressure maintains the poppet valve 36 in an open position during operation. When
the filter is serviced, back pressure closes the valve and prevents loss of fluid
from the outlet port 21. From the anti-drain poppet valve 36 the fluid enters outlet
flow passageway 38 and exists the filter through outlet port 21.
[0015] When the differential pressure across the filter element due to clogging with contaminants
exceeds a certain predetermined minimum, a spring biased by-pass valve 40 connecting
the inlet flow passageway 30 with the outlet flow passageway 38 will open to allow
fluid to flow through the filter assembly without passing through the filter element.
This by-pass valve 40 provides a safety feature which prevents hazardous pressure
build-up. Unfortunately, it also reduces the incentive to remove the canister 13 to
replace the filter element 23 since the fluid continues to flow normally even after
the filter element clogs. This lack of immediate serious consequences of filter clogging,
when coupled with the difficulty and inconvenience in removing canisters in prior
art designs, often resulted in a failure to periodically replace the filter element.
[0016] In accordance with an important aspect of the preferred embodiment at least one notch
44 or other abutment integral with the filter head 11 cooperates with the flared area
15a of the jackscrew 15 to create a second class lever fulcrum and bearing point arrangement
as illustrated in Figure 2 wherein a screwdriver is shown as the lever or other elongate
member itself. The notch 44 may be machined or cast into the filter head 11, or may
be formed in a block bolted or otherwise securely fastened to the filter head. The
latter approach might be employed in retrofit applications. The second class lever
utilizes its inherent mechanical advantage to create a powerful torque on the jackscrew
15 for the purpose of tightening or loosening the connection between the filter head
11 and the canister 13. The ability to use a screwdriver as a lever eliminates the
requirement of a special tool to remove the filter canister, as in prior art designs.
Often with such prior art designs, even if the special tool was available, the canister
was so tightly secured or frozen by corrosion and/or rust that removal of the canister
required a ritual of alternately tugging, yanking and vibration-tapping the casing
in an effort to free the frozen seal between the canister and filter head. With the
present invention, however, by employing a lever and its associated mechanical advantages,
a canister which otherwise might have proven difficult to remove can be loosened without
difficulty or frustration. The common, and almost always available screwdriver, is
well suited for use as the lever.
[0017] Referring to Figures 2 and 3, the notch 44 provides a recessed area in the filter
head 11 which receives the tip or blade portion 46a of a screwdriver 46 to provide
a fulcrum for the lever. The point of resistance for the lever is provided between
the screwdriver shaft 46b and the lugs or other spaced abutment means 48 in the flared
area 15a of jackscrew 15. When tightening the jackscrew 15, the lever force is applied
at the screwdriver handle 46c in a ratchet-like motion from left to right in Figure
2. Conversely, the screwdriver 46 shown in phantom-line in Figure 2, when moved right
to left in a ratchet-like motion, loosens the jackscrew 15 from its seated position
in the filter head 11.
[0018] It will be appreciated that although a screwdriver is particularly convenient for
providing the operative portion of the lever, any other appropriate device can be
substituted. For example, a simple steel rod of sufficient length and strength could
be used, provided its end could be received by the notch 44.
[0019] As illustrated by Figure 2, the lever (e.g. a screwdriver) is moved through an arc
centered about the notch 44. The torque applied to the jackscrew 15 is at its minimum
at the two end points of the lever's journey. The torque is maximized when the lever
occupies a vertical position as shown in Figure 2, or, more generally, occupies an
axial position parallel to the jackscrew's axis of rotation. If the lever engages
one of the lugs 48 which is at too great an angle from a vertical lever position,
the torque will be too small to be effective in loosening or tightening the jackscrew
15. Moreover, if the lever angle from vertical is too great, the threaded connection
between the jackscrew 15 and filter head 11 could be damaged as a result of the downward
force component.
[0020] Accordingly, the lugs 48, shown in Figure 3, should not be too few in number and,
consequently, spaced too far apart. They should instead be spaced close enough around
the perimeter of the jackscrew 15 so as to ensure one of the lugs 48 is within the
arc of the lever motion whose outer boundaries result in enough transferred torque
so as to effectively turn the jackscrew 15. Of course, spacing between the lugs 48
must be sufficiently wide to accommodate the lever throughout its full swing. Finally,
the jackscrew and the lugs thereon must obviously be of sufficient strength generally
to withstand the mechanical stress of the lever action.
[0021] By using an external thread on the jackscrew as illustrated, and thereby minimizing
its diameter, even jackscrews for large filter canisters are susceptible to fabrication
through stamping instead of the more expensive casting process which might be required
using the arrangement of US-A-4,316,801. It should also be noted that the arrangement
of Figure 1 allows for economical manufacturing processes throughout. For example,
the canister 13 has no critical inside diameters. In contrast, many prior art filter
assemblies, including that in US-A-4,316,801, have critical inside diameters, which
are more difficult to achieve.
[0022] From the foregoing, it will be appreciated that the filter assembly according to
the invention utilizes a lever mechanism to create a powerful torque on the jackscrew
so as to aid in the tightening and loosening of the canister and filter head connection.
The lever mechanism can be provided by an ordinary screwdriver which allows the filter
element to be replaced without difficulty and without special tools. As a result of
the easier servicing of the filter, periodic maintenance is more likely to be carried
out.
1. A filter assembly comprising a filter head (11) including a screw thread, and a
container (13) for receiving a filter element, the container being detachably and
sealingly secured to the filter head, adjacent to the screw-thread, characterized
by an annular screw-threaded member (15) screwed to the screw thread of the head (11)
and having spaced abutment means (15a), the head also having an abutment (44), both
the abutment of the head and the abutment means of the member (15) being engageable
by an elongate member (46) whereby a torque can be exerted on the annular screw-threaded
member to move it circumferentially relative to the head and permit relative motion
of the container along the axis of the screw-threads.
2. An assembly according to claim 1 characterized by means (13a,17) on the container
serving substantially to prevent movement of the jackscrew in the direction of the
axis of rotation of the jackscrew.
3. An assembly according to claim 1 or claim 2 characterized in that the abutment
on the head is a notch (44) which serves to receive a first end portion of the elongate
member (46) and providing a fulcrum therefor, and the abutment means of the screw-thread
member comprise a plurality of lugs (15) circumferentially spacedabout the perimeter
of said annular screw-threaded member such that one of said lugs serves to provide
a point of lever resistance for an intermediate portion of said elongate member whereby
said one lug responds to the application of force to a portion of the lever remote
from said notch by creating a mechanical advantage at said one lug which consequently
creates a torque on said annular screw-threaded member selectively to screw or unscrew
said annular screw-threaded member relative to said filter head allowing said filter
canister to move in the direction of the axis of rotation towards or away from respectively,
said filter head.
4. An assembly according to any one of claims 1 to 3 characterized in that the annular
screw-threaded member is externally-threaded and mates with an internal thread in
the filter head.
5. An assembly according to any one of claims 1 to 4 characterized in that the elongate
member is a screwdriver.
6. A filter assembly comprising a filter head (11) and a canister (13) for receiving
a filter element (23) through an open end thereof, characterized by a ring (15) mounted
proximate to said open end of said canister and being free to rotate about the periphery
of said canister, a notch (44) rigid with the head.., said ring comprising first means
(13a) for coupling said filter head and said ring whereby said canister is caused
to be operatively connected and sealed to said filterhead without requiring rotation
of said canister relative to the filter head, and second means (46) for tightening
or loosening the coupling between said ring (15) and said filter head (11) provided
by the first means, said second means being engageable with said filter head notch
to form a second class lever the fulcrum end of which lies at said notch and the point
of resistance of which is located on said second means.
7. A filter assembly according to claim 6 characterized in that said second means
includes a plurality of lugs (15a) extending about the radial periphery of said ring
and each providing a selected said point of resistance on said ring (15) for said
second class lever.
8. A filter assembly according to claim 6, or claim 7 characterized in that said second
class lever (46) is movable between at least a first and second position so as to
apply a torque to said ring, causing said ring (15) to rotate.
9. A filter assembly according to claim 8 characterized in that the torque applied
to said ring (15) increases from said first position to a maximum when said lever
(46) is positioned such that its longitudinal axis is parallel with the rotational
axis of said ring.
10. An assembly according to any one of claims 1 to 9, characterized by resilient
means (21) mounted in the head (11) which serve to bias the filter element (23) away
from the head.